Field of the Invention
The present invention relates to a focus detection apparatus and a control method for the same, and in particular relates to a focus detection apparatus capable of performing automatic focus adjustment, and a control method for the same.
Description of the Related Art
Single-lens reflex cameras are often provided with a focus detection system that uses a phase difference detection method to detect the focus state (defocus value) of the imaging optical system based on the phase difference between a pair of images formed by light that passed through the imaging optical system in an interchangeable lens. In this phase difference detection method, there is a risk of not being able to accurately detect the in-focus position due to the influence of the environment or the like at the time of imaging, and due to manufacturing error in single-lens reflex cameras and interchangeable lenses.
In order to solve this problem, Japanese Patent Laid-Open No. 2005-227639 discloses an image capturing apparatus that has a function (AF micro adjustment) for allowing the user to make desired micro adjustments to a correction value for the automatic focus adjustment function (AF). However, the conventional technology disclosed in Japanese Patent Laid-Open No. 2005-227639 has an issue in that the operations of image capturing and checking need to be performed repeatedly in order to check whether or not the result of the user's micro adjustment is correct.
In order to resolve this issue, Japanese Patent Laid-Open No. 2005-109621 discloses an image capturing apparatus that has a function in which the defocus value of the imaging lens is associated with images, and an AF correction value is automatically calculated based on a focus position shift amount associated with an image determined by the user to be in focus.
In Japanese Patent Laid-Open No. 2005-109621, the focus position shift amount is obtained according to the AF bracket step amount and the bracket count, and there is a possibility that when defocus values are detected at various lens positions, there will not be a match with the aforementioned focus position shift amount due to various causes of error. In view of this, in order to obtain a more precise AF correction value, it has been envisioned to detect the defocus value at various lens positions and calculate the AF correction value based on the detected defocus values. However, due to causes of error such as error in the detection of defocus values associated with images and error in image selection, there is a risk of obtaining an erroneous AF correction value, and the focus adjustment precision easily degrading.